WO2007034966A1

WO2007034966A1 - Projection-use zoom lens

Info

Publication number: WO2007034966A1
Application number: PCT/JP2006/319081
Authority: WO
Inventors: Takeshi Kitakata; Takahiro Sugiyama
Original assignee: Brother Kogyo Kabushiki Kaisha
Priority date: 2005-09-26
Filing date: 2006-09-26
Publication date: 2007-03-29
Also published as: US20100149655A1

Abstract

A zoom lens having fewer constituting lenses and easily keeping telecentricity. A first lens group (G1) through a fourth lens group (G4) are disposed sequentially from a projection plane (PL) side. The first lens group (G1) consists of three lenses, a negative lens, a positive lens and a negative lens sequentially from the projection plane (PL) side, and has a negative power. The second lens group (G2) consists of a total of three lenses, one positive lens, one junction lens and one junction lens sequentially from the projection plane (PL) side, and has a positive power. The third lens group (G3) consists of one negative lens. The fourth lens group (G4) consists of one positive lens. At power varying, the first lens group (G1) and the second lens group (G2) are moved with the third lens group (G3) and the fourth lens group (G4) kept fixed. The third lens group (G3) is moved for focusing.

Description

Specification

Zoom lens for projection

Technical field

[0001] The present invention relates to a zoom lens used in a projection optical system.

Background art

Conventionally, various types of optical systems have been proposed as projection zoom lenses.

For example, there are those described in Patent Documents 1 to 5 below.

[0003] However, the optical systems described in these documents have the disadvantage that not only the lens cost becomes high, but the lens system becomes large. In this specification, the total number of cemented lenses equivalent to a single lens in terms of power is counted as one. “A cemented lens equivalent to a single lens in terms of power” is a cemented lens in which the scales of the lens surfaces to be joined are the same. In general, lenses constituting such a cemented lens can be achromatic by making the refractive index different between adjacent lenses. However, in the present specification, even if the refractive indexes between lenses are the same, if the Rs of the lens surfaces to be joined are the same, they are assumed to be “a cemented lens equivalent to a single lens in terms of power”.

[0004] For the purpose of taking into account the light emission characteristics of the image element (that is, if the light incident on the optical element component such as a liquid crystal or a prism has an angle, it has polarization characteristics, changes its color, or reflects it. Therefore, the projection zoom lens is preferably designed to give telecentricity (particularly image side telecentricity). On the other hand, in a projection zoom lens, the focusing is generally performed with a lens close to an image element. For this reason, conventional focusing lenses must also take telecentricity into consideration. For example, in recent years, a condenser lens is generally disposed immediately in front of an image element in order to project a larger amount of light from the image element and to reduce the lens system. If the focusing lens arranged in is composed of positive lenses, there will be a problem if the telecentricity is impaired.

Patent Document 1: Japanese Patent Application Laid-Open No. 2004-77950 Patent Document 2: JP 2004-54021 A

Patent Document 3: Japanese Patent Laid-Open No. 2003-215453

Patent Document 4: Japanese Unexamined Patent Publication No. 2003-215455

Patent Document 5: Japanese Unexamined Patent Publication No. 2000-292698

Disclosure of the invention

Problems to be solved by the invention

[0005] The present invention has been made in view of the above situation. One object of the present invention is to provide a zoom lens for projection that has a smaller number of lens elements than conventional lenses. Another object of the present invention is to provide a zoom lens for projection that can easily maintain telecentricity.

Means for solving the problem

In order to achieve the above object, in a zoom lens according to one aspect of the present invention, a first lens group, a second lens group, a third lens group, in order from the projection plane, Consists of a fourth lens group, and enables zooming between the short and long focal ends. The first lens group includes a negative lens, a negative lens, a positive lens, and a negative lens in order from the projection surface side, and has a negative number. The second lens group consists of a total of three lenses, one cemented lens or one positive lens, one positive lens or one cemented lens, and one cemented lens in order from the projection surface side. This lens has a positive power. The third lens group is composed of one negative lens. The fourth lens group is composed of one positive lens. Further, at the time of zooming, the first lens group and the second lens group are moved, and the third lens group and the fourth lens group are fixed. In addition, the third lens group is configured to be moved for focusing!

In this zoom lens, the focal length is variable by moving the first lens group and the second lens group. Also, with this zoom lens, focusing can be achieved by moving the third lens group.

[0008] The fourth lens group is a condenser lens for projecting more light from the image element and at the same time reducing the outer diameter of the lens system. In the present invention, the optical system from the first lens group to the fourth lens group is configured to maintain telecentricity. In addition, Maintaining telecentricity means a state in which the principal ray and the optical axis are almost parallel (including an inclination of about ± 10 °).

[0009] The zoom lens of the present invention may satisfy the following conditional expression (1).

[0010] 0.7≤ I f / ϊ I ≤1.5 (1)

twenty one

Where f is the composite focal length of the first lens unit

f: Composite focal length of the second lens group

2

The zoom lens of the present invention may satisfy the following conditional expression (2).

[0011] 1.5≤ I f / f I ≤2.5 (2)

b w

Where f is the combined back focus up to the first lens group and the third lens group

b

f: Focal length at short focal end

w

The zoom lens of the present invention may satisfy the following conditional expression (3).

[0012] 0.08≤ I f / f

T 3 I ≤0.3 (3)

Where f is the composite focal length of the third lens group

Three

f

T: Focal length at the long focal end

The projector according to the present invention includes the zoom lens according to the present invention described above.

Hereinafter, the conditional expressions (1) to (3) will be described.

Conditional expression (1) is a condition for regulating the relationship between the focal lengths of the first lens unit and the second lens unit that move to change the focal length. I f / f

2 1 I force When the value exceeds the lower limit of 0.7, the focal length of the first lens group becomes too large, and the amount of movement of the first and second lens groups for changing the focal length becomes large. As a result, the lens system becomes large, which is not preferable.

[0015] Also, | f Zf I force upper limit of 1.5, to make the lens smaller when larger than 5

twenty one

Is advantageous, but the focal length force s of the first lens group becomes too small, so that the spherical aberration generated in the first lens group becomes excessive. Then, it becomes difficult to correct spherical aberration satisfactorily.

[0016] Conditional expression (2) indicates that the first lens group force and the third lens group have the required magnitude of the combined back focus, and the third lens group and the fourth lens Lens group This is a condition for securing an air space in which the illumination optical system can be inserted between the two. | f / f

If b w I is smaller than the lower limit of 1.5, the air space between the third lens group and the fourth lens group becomes too small, and the illumination optical system cannot be inserted.

[0017] Also, when f / f I is larger than the upper limit of 2.5, the illumination optical system is inserted.

This is advantageous for securing the air gap between the third lens group and the fourth lens group, but the focal length force S of the negative lens of the first lens group and the third lens group becomes too small, resulting in coma. Increase in aberrations is preferable.

[0018] Conditional expression (3) is a condition for maintaining the telecentricity of the optical system appropriately in an optical system in which focusing is performed by the third lens group and a condenser lens is installed immediately before the image element. . | When f / f I is smaller than the lower limit 0.08, the focus of the third lens group

T 3

The distance is too large. Then, the amount of movement of the third lens group when focusing is too large, and as a result, the lens group becomes large, which is preferable.

[0019] When I f / f I exceeds the upper limit of 0.3, the third lens group for focusing

T 3

The amount of movement is small, which is advantageous for reducing the size of the lens system. However, in this case, not only is it difficult to maintain the telecentricity of the lens system, but the spherical aberration is over, which is not preferable.

[0020] A zoom lens according to another aspect of the present invention includes a first lens group, a second lens group, and a third lens group in order of the projection surface side force, and includes a short focal end and a long focal end. It is possible to zoom in between. The first lens group is composed of three lenses of a negative lens, a positive lens, and a negative lens in order from the projection surface side, and has a negative power. The second lens group includes, in order from the projection surface side, one positive lens, one cemented lens composed of two lenses, and one cemented lens composed of two lenses. It is composed of a total of 3 lenses and has positive power. The third lens group is composed of two lenses of a negative lens and a positive lens in order, and has a positive power. In the zoom lens according to the present invention, the first lens group and the second lens group are moved during zooming, and the third lens group is fixed. The third lens group can be moved for focusing.

In this zoom lens, the focal length is changed by moving the first lens group and the second lens group. The separation is variable. Also, with this zoom lens, focusing can be achieved by moving the third lens group.

In the present invention, the telecentricity can be maintained by the optical system up to the third lens group by using a design that satisfies conditional expressions (4) to (6) described later. it can. Note that maintaining telecentricity means that the principal ray and the optical axis are almost parallel (including an inclination of about ± 10 °).

[0023] The zoom lens of the present invention may satisfy the following conditional expression (4).

0.6≤ I f / ϊ I ≤1.3 (4)

twenty one

Where f is the composite focal length of the first lens unit

f: Composite focal length of the second lens group

2

The zoom lens of the present invention may satisfy the following conditional expression (5). 0. 8≤ I f / ϊ I ≤1. 8 (5)

b w

b

f: Focal length at short focal end

w

The zoom lens of the present invention may satisfy the following conditional expression (6). 0.08≤ \ ϊ / ϊ \ ≤0.3 (6)

t 3

Where f is the composite focal length of the third lens group

Three

f: Focal length at long focal end

Hereinafter, the conditional expressions (4) to (6) will be described.

Conditional expression (4) is a condition for regulating the relationship between the focal lengths of the first lens unit and the second lens unit that move to change the focal length. Now, condition I f / f I force lower limit 0.6

twenty one

When it is smaller than, the focal length of the first lens group becomes too large, and the amount of movement of the first lens group and the second lens group for changing the focal length becomes large. As a result, the lens system becomes large, which is not preferable.

[0026] Also, if the I f / f I force upper limit is greater than 1.3, to reduce the size of the lens

twenty one

Is advantageous, but the focal length force s of the first lens group becomes too small. The spherical aberration generated in is excessive. Then, it becomes difficult to correct spherical aberration satisfactorily.

[0027] Conditional expression (5) indicates that the first lens group force and the third lens group are combined with the third lens group and the image element in order to ensure the combined back focus up to the third lens group to a required magnitude and to ensure an appropriate amount of light for the projected image. This is a condition for ensuring an air gap between which the illumination optical system can be inserted. Now I f b Zf w

When I is smaller than the lower limit O. 8, the air space between the third lens group and the image element becomes too small, and the illumination optical system cannot be inserted.

[0028] When I ί / ί I is larger than the upper limit of 1.8, the illumination optical system is inserted. B w

This is advantageous for securing the air gap between the third lens group and the image element, but the focal length force S of the negative lens of the first lens group and the third lens group becomes too small, resulting in coma aberration. It ’s growing! /.

Conditional expression (6) is a condition for performing focusing with the third lens group and maintaining the telecentricity of the lens system appropriately. Now, when | f t / f 3 I is smaller than the lower limit of 0.08, the focal length of the third lens unit becomes too large. Then, the amount of movement of the third lens group when focusing is too large, and as a result, the lens group becomes large, which is preferable.

[0030] When f / f I is larger than the upper limit of 0.3, t 3 of the third lens group for focusing is set.

The amount of movement is small, which is advantageous for reducing the size of the lens system. However, in this case, not only is it difficult to maintain the telecentricity of the lens system, but the spherical aberration becomes under, which is not preferable.

The invention's effect

[0031] According to the present invention, it is possible to provide a zoom lens for projection with eight lens elements, which is smaller than in the past. In addition, according to the present invention, it is possible to provide a zoom lens for projection that can easily maintain telecentricity.

Brief Description of Drawings

FIG. 1 is an explanatory diagram showing a lens configuration of Numerical Example 1 according to the first embodiment.

FIG. 2 is a diagram showing various aberrations at the short focal end in Numerical Example 1 of the first embodiment.

FIG. 3 is a diagram showing various aberrations at an intermediate focal position in Numerical Example 1 of the first embodiment.

FIG. 4 is a diagram showing various aberrations at the long focal end in Numerical Example 1 according to the first embodiment. [5] FIG. 5 is an explanatory diagram showing a lens configuration of Numerical Example 2 of the first embodiment.

6] Various aberration diagrams at the short focal end in Numerical Example 2 according to the first embodiment.

7] Various aberration diagrams at the intermediate focal position in Numerical Example 2 of the first embodiment. 8] Various aberration diagrams at the long focal end in Numerical Example 2 of the first embodiment.

9] An explanatory diagram showing the lens configuration of Numerical Example 3 of the first embodiment. FIG.

FIG. 10] Various aberration diagrams at the short focus end in Numerical Example 3 according to the first embodiment. 11] Various aberration diagrams at the intermediate focal position in Numerical Example 3 of the first embodiment. 12] Various aberration diagrams at the long focal end in Numerical Example 3 of the first embodiment. 13] An explanatory diagram showing the lens configuration of Numerical Example 1 of the second embodiment. FIG.

14] Various aberration diagrams at the short focal end in Numerical Example 1 according to the second embodiment. 15] Various aberration diagrams at the intermediate focal position in Numerical Example 1 of the second embodiment. FIG. 16] Various aberration diagrams at the long focal end in Numerical Example 1 according to the second embodiment. 17] An explanatory diagram showing the lens configuration of Numerical Example 2 of the second embodiment. FIG.

18] Various aberration diagrams at the short focal end in Numerical Example 2 of the second embodiment. 19] Various aberration diagrams at the intermediate focal position in Numerical Example 2 of the second embodiment. 20] Various aberration diagrams at the long focal end in Numerical Example 2 of the second embodiment.圆 21] An explanatory diagram showing the lens configuration of Numerical Example 3 of the second embodiment.

圆 22] Various aberration diagrams at the short focus end in Numerical Example 3 of the second embodiment.圆 23] Various aberration diagrams at the intermediate focal position in Numerical Example 3 of the second embodiment. 24] Various aberration diagrams at the long focal end in Numerical Example 3 of the second embodiment. FIG. 25 is an explanatory diagram showing a lens configuration of Numerical Example 1 according to the third embodiment.

26] Various aberration diagrams at the short focal end in Numerical Example 1 according to the third embodiment. 27] Various aberration diagrams at the intermediate focal position in Numerical Example 1 of the third embodiment. FIG. 28 is an aberration diagram at the long focal end in Numerical Example 1 of the third embodiment. 29] FIG. 29 is an explanatory diagram showing a lens configuration of Numerical Example 2 according to the third embodiment.

30] Various aberration diagrams at the short focal end, in Numerical Example 2 of the third embodiment. 31] Various aberration diagrams at the intermediate focal position in Numerical Example 2 of the third embodiment. FIG. 32] Various aberration diagrams at the long focal point in Numerical Example 2 of the third embodiment. FIG. 33 is an explanatory diagram showing a lens configuration of Numerical Example 3 according to the third embodiment.

FIG. 34 is a diagram illustrating various aberrations at the short focal end in Numerical Example 3 according to the third embodiment.

FIG. 35 is a diagram showing various aberrations at an intermediate focal position in Numerical Example 3 of the third embodiment.

FIG. 36 is a diagram illustrating various aberrations at the long focal end in Numerical Example 3 according to the third embodiment.

Explanation of symbols

[0033] G first lens group

G Second lens

2 groups

G

3 Third lens group

G

4 Fourth lens group

PL projection surface

CD image sensor

GL image sensor protective glass

BEST MODE FOR CARRYING OUT THE INVENTION

[0034] (First embodiment)

First, the zoom lens according to the first embodiment will be described. The zoom lens of the first embodiment is composed of a first lens group, a second lens group, a third lens group, and a fourth lens group in order from the projection plane side, and includes a short focal end and a long focal end. The first lens group consists of three lenses, a negative lens, a positive lens, and a negative lens, in order from the projection plane side, and has negative power. The second lens unit is composed of a total of three lenses, one cemented lens, one positive lens, and one cemented lens, in order of the projection surface side force. The third lens group is composed of one negative lens, the fourth lens group is composed of one positive lens, and the first lens is used for zooming. The lens group and the second lens group are moved, and the third lens group and the fourth lens group are fixed. The third lens group is a preparative Ru zoom lens arrangement is moved for focusing.

Next, specific numerical examples regarding the first embodiment will be described.

(Configuration of Numerical Example 1 in the First Embodiment)

The configuration of the zoom lens according to Numerical Example 1 of the first embodiment is shown in FIG. Figure 1 Symbol PL is the projection plane, Symbol GL is the protective glass of the image sensor (which may include an optical filter, etc.), Symbol CD is the image sensor, Symbol G is the first lens group, and Symbol G is

1 2 The second lens group, symbol G represents the third lens group, and symbol G represents the fourth lens group. Also note

3 4

The number R indicates the diaphragm surface.

[0037] This zoom lens includes a first lens group G, a second lens group G, and the like in order from the projection plane PL side.

1 2

The third lens group G and the fourth lens group G are arranged between the short focal end and the long focal end.

3 4

This is a zoom lens capable of zooming.

[0038] The first lens group G is composed of three lenses of a negative lens, a positive lens, and a negative lens in order from the projection plane PL side, and has negative power. Here, as described above, one lens as a unit constituting each lens group includes a case where it is a cemented lens equivalent to a single lens in terms of power. Here, the cemented lens is obtained by cementing two or more single lenses.

[0039] The second lens group G includes one cemented lens (R to R) and one sheet in order from the projection plane PL side.

2 8 10 Consists of positive lens (R to R) and one cemented lens (R to R) and has positive power.

11 12 13 15

is doing. In the first embodiment, each of these cemented lenses is composed of two lenses. Each of the above-described cemented lenses may be composed of three or more lenses, either one or both of which are two lenses. Also, the single positive lens (R to R) mentioned above is

11 12

Alternatively, it may be constituted by a cemented lens.

[0040] The third lens group G is composed of one negative lens. This negative lens also has negative power

Three

Even a cemented lens with.

The fourth lens group G is composed of one positive lens. This positive lens is also positive power

Four

Even a cemented lens with.

[0042] Therefore, the zoom lens of the first embodiment is composed of eight lenses as a whole. As described above, here, a cemented lens equivalent to a single lens in terms of power is counted as one lens.

In the first embodiment, the first lens group G and the second lens group G are used for zooming.

1 2 is moved, and the third lens group G and the fourth lens group G are fixed.

3 4

Yes. Furthermore, in the first embodiment, the third lens group G is moved for focusing. It becomes the composition which becomes. Since the lens group moving mechanism itself is the same as the conventional one, a detailed description thereof will be omitted.

[0044] (Characteristics of Numerical Example 1 in First Embodiment)

Various aberrations in Numerical Example 1 are shown in FIGS. Fig. 2 shows various aberrations at the short focal end of Numerical Example 1, and Fig. 3 shows various aberrations at the intermediate focal position in Numerical Example 1.

4 is a diagram of various aberrations at the long focal end of Numerical Example 1. FIG.

[0045] In these drawings, symbols G, B, and R in chromatic aberration represented by spherical aberration are spherical aberrations for green, blue, and red wavelengths, respectively, and symbol SC is an unsatisfactory sine condition. .

In the astigmatism, the symbol S is sagittal and the symbol M is meridional.

[0047] Table 1 shows various characteristics of Numerical Example 1.

[0048] [Table 1]

R Nd Vd

1 2.00 1.80420 46.5

2 27.702 9.90

3 -120.986 4.09 1.80420 46.5

4 -49.048 8.53

5 -31.433 1.50 1.48749 70.

6 24. 30 29.54

7 8.00

8 141.659 1.50 1.83400 37.3

9 25.491 6.22 1.80420 46.5

n i

10 -58.563 .10

11 24.9 o17 5.00 1.83400 37.3

12 32.667 10.90

13 37.268 1.00 1.80518 25.4

14 7.49 1.48749 70.4

15 -48.389 2.51

16 -20.814 1.62 1.48749 70.

17 -28.034 25.00

18 49.471 5.48 1.58913 61.2

19

In Table 1, symbol R is the radius of curvature, symbol d is the lens thickness or air spacing, symbol Nd is the refractive index of the d-line (588 nm), symbol Vd is the Abbe number of the d-line (the Abbe number is the symbol Vd) May also be expressed). The relationship between the subscripts R and d and the lens is as shown in Fig. 1. Table 1 The symbol f in the figure is the focal length of the first lens group G, and the symbol f is the focal length of the second lens group G.

1 1 2 2

The symbol f indicates the focal length of the third lens group G.

3 3

[0050] Further, in Table 1, the symbol f is the focal length of the short focal end, the symbol f is the focal length of the long focal end, and w Γ

The symbol f indicates the combined back focus from the first lens group G force to the third lens group G b 1 3

[0051] Further, the projection distance in the first embodiment is 1000 mm.

[0052] According to the zoom lens of Numerical Example 1, it is possible to provide a projection zoom lens having eight lens elements, which is smaller than the conventional zoom lens. As described above, the number of cemented lenses equivalent to a single lens in terms of power is calculated as one. In addition, this zoom lens can easily maintain telecentricity even in an optical system in which a condenser lens (that is, the fourth lens group G) is disposed immediately in front of the image element by forming the focusing lens with a negative lens. Toi

Four

There are advantages. The telecentricity obtained in this example is as shown in Table 1.

The zoom lens according to the first embodiment can be used as a projection lens for a projector.

(Configuration of Numerical Example 2 in the First Embodiment)

Next, FIG. 5 shows a configuration of a zoom lens according to Numerical Example 2 of the first embodiment. In addition

In the description of Numerical Example 2, the same reference numerals are used for the same components and characteristics as those of Numerical Example 1 to simplify the description.

[0055] Various aberrations of Numerical Example 2 are shown in FIGS. Fig. 6 shows various aberrations at the short focal end, and Fig. 7 shows

FIG. 8 is a diagram of various aberrations at the long focal end. Table 2 shows the characteristics of Numerical Example 2.

[0056] [Table 2] R d Nd Vd

1 49.812 2.00 1.80420 46.50

2 27.023 11.68

3 -63.436 5.55 1.80420 46.50

4 11.60

5 -27.450 1.50 1.48749 70.45

6 96.853 25.47

7 8.00

8 -123.785 10.00 1.83400 37.34

9 22.04 o6 10.00 1.80420 46.50

10 .10

11 32.230 3.05 1.83400 37.34

12 95.673

13 39.478 4.80 1.80518 25.46

14 15.316 6.7 o6 1.48749 70.45

o

15 -99.727 2.25

16 -29.264 1.63 1.48749 70.45

17 -45.890 22.00

18 54.598 9.00 1.58913 61.25

19

[0057] Other configurations and advantages of the numerical example 2 are basically the same as those of the numerical example 1, and thus detailed description thereof is omitted.

(Configuration of Numerical Example 3 in the First Embodiment) Next, FIG. 9 shows a configuration of a zoom lens according to Numerical Example 3 of the first embodiment. In the description of Numerical Example 3, the same reference numerals are used for the same components and characteristics as those of Numerical Example 1 to simplify the description.

[0059] Various aberrations of Numerical Example 3 are shown in FIGS. Figure 10 shows various aberrations at the short focal end.

11 shows various aberrations at the intermediate focal position, and FIG. 12 shows various aberrations at the long focal end. Table 3 shows the characteristics of Numerical Example 3.

[0060] [Table 3]

R d Nd Vd

1 2.00 1.80420 46.50

2 29.385 11.51

3 5.66 1.80420 46.50

4 -35.000 10.64

5 1.50 1.48749 70.45

6 -243.798 38.35

m

7 oo 8.00

8 205.4 ∞18 1.51 1.83400 37.34

9 39.209 4.45 1.80420 46.50

10 -83.634. 15

11 29.225 2.60 1.83400 37.34

12 52.209 15.00

13 39.659 1.00 1.80518 25.46

14 15.610 6.52 1.48749 70.45

15 -123.274 3.29

16-19.842 2.22 1.48749 70.45

17 -22.580 22. 11

18 50.627 8.86 1.58913 61.25

19

[0061] Other configurations and advantages of the numerical value example 3 are basically the same as those of the numerical value example 1, and thus detailed description thereof is omitted.

[0062] (Second Embodiment) Next, a zoom lens according to the second embodiment will be described. The zoom lens of the second embodiment is composed of a first lens group, a second lens group, a third lens group, and a fourth lens group in order from the projection plane side, and includes a short focal end and a long focal end. The first lens group consists of three lenses, a negative lens, a positive lens, and a negative lens, in order from the projection plane side, and has negative power. The second lens group is composed of a total of three lenses, one positive lens, one cemented lens, and one cemented lens, in order of the projection surface side force. The third lens group is composed of one negative lens, the fourth lens group is composed of one positive lens, and the first lens is used for zooming. The lens group and the second lens group are moved, and the third lens group and the fourth lens group are fixed. The third lens group is a preparative Ru zoom lens arrangement is moved for focusing.

Next, specific numerical examples regarding the zoom lens according to the second embodiment will be described.

(Configuration of Numerical Example 1 in Second Embodiment)

FIG. 13 shows a configuration of a zoom lens according to Numerical Example 1 of the second embodiment. In FIG. 13, symbol PL is the projection plane, symbol GL is the protective glass of the image sensor (which may include an optical filter, etc.), symbol CD is the image sensor, and symbol G is the first lens group. , Sign G

11 12 denotes the second lens group, G denotes the third lens group, and G denotes the fourth lens group. Also

13 14

The symbol R indicates the diaphragm surface.

27

[0065] This zoom lens includes a first lens group G and a second lens group G in order from the projection plane PL side.

11 12 and the third lens group G and the fourth lens group G, between the short focus end and the long focus end.

13 14

This is a zoom lens capable of zooming.

[0066] The first lens group G includes three lenses, a negative lens, a positive lens, and a negative lens, in that order from the projection plane PL side.

11

The lens has a negative power. Here, as described above, one lens as a unit constituting each lens group includes a case where it is a cemented lens equivalent in power to a single lens. Here, the cemented lens is obtained by cementing two or more single lenses.

[0067] The second lens group G includes, in order from the projection plane PL side, one positive lens (R to R) and one sheet

12 28 29 Consists of a cemented lens (R to R) and a single cemented lens (R to R). Have. In the second embodiment, each of these cemented lenses is composed of two lenses. Each of the above-described cemented lenses may be composed of three or more lenses that are joined by either one or both of the two forces. One positive lens (R to R)

28 29 may be constituted by a cemented lens.

[0068] The third lens group G includes one negative lens. This negative lens also has negative power

13

Even a cemented lens with.

[0069] The fourth lens group G is composed of one positive lens. This positive lens is also positive power

14

Even a cemented lens with.

Therefore, the zoom lens according to the second embodiment is composed of eight lenses as a whole. As described above, here, a cemented lens equivalent to a single lens in terms of power is counted as one lens.

In the second embodiment, the first lens group G and the second lens group G are used for zooming.

11

And the third lens group G and the fourth lens group G are fixed.

12 13 14

ing. Further, in the second embodiment, the third lens group G is moved for focusing.

13

It becomes the structure that is made. Such a lens group moving mechanism itself is the same as in the prior art, so a detailed description thereof will be omitted.

(Characteristics of Numerical Example 1 in Second Embodiment)

Various aberrations in Numerical Example 1 are shown in FIGS. FIG. 14 shows various aberrations at the short focal end of Numerical Example 1, FIG. 15 shows various aberrations at the intermediate focal position of Numerical Example 1, and FIG. 16 shows various aberrations at the long focal end of Numerical Example 1. It is.

[0073] In these drawings, symbols G, B, and R in the chromatic aberration represented by spherical aberration are spherical aberrations for green, blue, and red wavelengths, respectively, and symbol SC is an unsatisfactory sine condition. .

In the astigmatism, the symbol S is sagittal and the symbol M is meridional.

[0075] Table 4 shows properties of Numerical Example 1.

[0076] [Table 4] R d Nd Vd

1 53.422 2.00 1.80420 46.50

2 31.362 7.05

3 4655.051 4.72 1.83400 37.34

4 -64.540 12.17

5 -24.417 1.50 1.80420 46.50

6 35.805 11.77

7 ∞ 6.25

8 -39.319 10.00 1.83400 37.34

9 -27.573 .10

10 30.844 1.52 1.78472 25.70

11 26.891 3.76 1.83400 37.34

12 107.402 7.79

13 5.00 1.80518 25.46

14 14.524 8.81 1.64250 57.96

15 -60.800 2.16

16 -26.076 7.35 1.59551 39.23

17 -41.012 29.41

18 24.036 9.00 1.58913 61.25

19 oo

In Table 4, R is the radius of curvature, d is the lens thickness or air spacing, Nd is the refractive index of the d line (588 nm), Vd is the Abbe number of the d line (the Abbe number is V d May also be expressed). The relationship between the subscripts R and d and the lens is as shown in FIG. In Table 4, the symbol f is the focal length of the first lens group G, the symbol f is the focal length of the second lens group G, The symbol f indicates the focal length of the third lens group G.

3 13

[0078] Further, in Table 4, the symbol f is the focal length of the short focal end, the symbol f is the focal length of the long focal end, and w Γ

Symbol f indicates the combined back focus up to the first lens group G force and the third lens group G b 11 13

The

In addition, the projection distance in the second embodiment is 1000 mm.

[0080] According to the zoom lens of Numerical Example 1, it is possible to provide a projection zoom lens having eight lens elements, which is smaller than the conventional zoom lens. As described above, the number of cemented lenses equivalent to a single lens in terms of power is calculated as one. In addition, this zoom lens can easily maintain telecentricity even in an optical system in which a condenser lens (that is, the fourth lens group G) is arranged immediately in front of the image element by forming the focusing lens as a negative lens. When

14

There is an advantage. The telecentricity obtained in this example is as shown in Table 1.

[0081] The zoom lens of the second embodiment can be used as a projection lens of a projector.

(Configuration of Numerical Example 2 in the Second Embodiment)

Next, FIG. 17 shows a configuration of a zoom lens according to Numerical Example 2 of the second embodiment. In the description of Numerical Example 2, the same reference numerals are used for the same constituent elements and characteristics as those of Numerical Example 1 to simplify the description.

[0083] Various aberrations of Numerical Example 2 are shown in FIGS. Figure 18 shows various aberrations at the short focal end.

19 shows various aberrations at the intermediate focal position, and FIG. 20 shows various aberrations at the long focal end. Table 5 shows the characteristics of Numerical Example 2.

[0084] [Table 5] R d Nd Vd

1 93.331 2.0000 1.83400 37.34

2 29.640 13.20

3 -36.805 2.88 1.84666 23.83

4 -31.060 18.72

5 .-29.859 8.00 1.69350 53.54

6 29.21

7 oo 10.00

8 114.321 2.48 1.80420 46.50

9 -114.606 .10

10 31.687 o 1.50 1.53172 48.83

11 25.212 4.34 1.80420 46.50

12 51.363 12.01

13 41.094 1.00 1.80518 25.46

14 13.966 9.41 1.51823 58.96

15 2.47

16 -29.699 2.03 1.84666 23.83

17 22.00

18 49.338 9.00 1.58913 61.25

19

Since the other configurations and advantages of Numerical Example 2 are basically the same as those of Numerical Example 1, further detailed description thereof is omitted.

(Configuration of Numerical Example 3 in the Second Embodiment) Next, FIG. 21 shows a configuration of a zoom lens according to Numerical Example 3 of the second embodiment. In the description of Numerical Example 3, the same reference numerals are used for the same components and characteristics as those of Numerical Example 1 to simplify the description.

Various aberrations of Numerical Example 3 are shown in FIGS. Figure 22 is a diagram of various aberrations at the short focal end.

23 shows various aberrations at the intermediate focal position, and FIG. 24 shows various aberrations at the long focal end. Table 6 shows the characteristics of Numerical Example 3.

[0088] [Table 6]

R d Nd Vd

1 84.522 2.00 1.83400 37.34

2 29.492 12.95

3 -38.598 3.03 1.84666 23.83

4 -32.059 13.21

5 .-30.942 8.00 1.58913 61.25

6 -66.740 36.97

7 oo 10.00

8 130.736 2.56 1.80420 46.50

9 -92.881 .10

10 28.248 1.50 1.53172 48.83

11 21.278 6.75 1.80420 46.50

12 37.032 8.43

13 47.725 1.00 1.80518 25.46

14 13.505 7.36 1.51823 58.96

15 -315.881 3.66

16-19.104 1.84 1.84666 23.83

17 22.00

18 35.522 9.00 1.58913 61.25

19

Since the other configurations and advantages of Numerical Example 3 are basically the same as those of Numerical Example 1, further detailed description thereof is omitted.

[0090] (Third embodiment)

First, the zoom lens according to the third embodiment will be described. Zoom lens according to the third embodiment The zoom lens is composed of a first lens group, a second lens group, and a third lens group in order from the projection surface side, and is capable of zooming between the short focal end and the long focal end. The first lens group is composed of three lenses, a negative lens, a positive lens, and a negative lens, in order from the projection surface side, and has a negative power. The second lens group is a projection lens. In order of surface force, it consists of a total of 3 lenses: 1 positive lens, 1 cemented lens composed of 2 lenses, and 1 cemented lens composed of 2 lenses The third lens group is composed of two lenses, a negative lens and a positive lens in order from the projection surface side, and has a positive power. In this case, the first lens group and the second lens group are moved, and the third lens group is fixed. _{The three} lens group is a zoom lens configured to be moved for focusing.

Next, specific numerical examples regarding the zoom lens according to the third embodiment will be described.

(Configuration of Numerical Example 1 in the Third Embodiment)

FIG. 25 shows a configuration of a zoom lens according to Numerical Example 1 of the third embodiment. In FIG. 25, symbol PL is the projection plane, symbol GL is the protective glass for the image element, symbol CD is the image element, symbol G is the first lens group, symbol G is the second lens group, and symbol G is the third lens group. Shows

21 22 23

The The symbol R indicates the diaphragm surface.

47

This zoom lens includes a first lens group G and a second lens group G in order from the projection plane PL side.

21 22 and the third lens group G, and zooming between the short and long focal ends is possible.

twenty three

Zoom lens.

[0094] The first lens group G includes three lenses, a negative lens, a positive lens, and a negative lens, in that order from the projection plane PL side.

twenty one

The lens has a negative power. Here, unless otherwise specified, one lens as a unit constituting each lens group includes a case where it is a single lens and a case where it is a cemented lens. Here, the cemented lens is obtained by cementing two or more single lenses.

[0095] The second lens group G includes, in order from the projection plane PL side, one positive lens and two cemented lenses (

twenty two

Lens between R and R) and has a positive power. In this third example,

50 55

These cemented lenses are both composed of two single lenses.

[0096] The third lens group G is composed of two lenses, a negative lens and a positive lens, in this order from the projection plane PL side. Have positive power. These lenses are single lenses in the third embodiment. However, these lenses can also be cemented lenses.

As described above, the zoom lens of the third example is composed of eight lenses as a whole. Here, a cemented lens equivalent to a single lens in terms of power is counted as one lens.

In the third embodiment, the first lens group G and the second lens group G are used for zooming.

twenty one

And the third lens group G is fixed. In addition, book

22 23

In the third embodiment, the third lens group G is configured to be moved for focusing.

twenty three

It is. Since such a lens group moving mechanism itself may be the same as the conventional one, a detailed description thereof will be omitted.

[0099] (Characteristics of Numerical Example 1 in Third Embodiment)

Various aberrations in Numerical Example 1 are shown in FIGS. FIG. 26 shows various aberrations at the short focal end of Numerical Example 1, FIG. 27 shows various aberrations at the intermediate focal position of Numerical Example 1, and FIG. 28 shows various aberrations at the long focal end of Numerical Example 1. It is.

[0100] In these figures, symbols G, B, and R in chromatic aberration represented by spherical aberration are spherical aberrations for the wavelengths of green, blue, and red, respectively, and symbol SC is an unsatisfactory sine condition. .

[0101] In the astigmatism, the symbol S indicates sagittal, and the symbol M indicates meridional.

[0102] Table 7 shows properties of Numerical Example 1.

[0103] [Table 7]

R d Nd Vd

1 134.090 2.00 1.80420 46.50

2 29.529 12.40

3 -42.882 8.00 1.80518 25.46

4 -33.046 5.85

5 -34.972 5.00 1.48749 70.44

6-99.671 45.00

7 ■ 5.59

8 208.874 3.32 1.80420 46.50

9 -92.178 1.50

10 34.064 1.30 1.80518 25.46

11 19.670 4.35 1.72000 43.90

12 78.337

13 29.821 1.00 1.84666 23.78

14 16.405 4.69 1.48749 70.44

15 -80.810 1.82

16 -35.233 1.30 1.48749 70.44

17 22.113 7.90

18 46.050 3.80 1.77250 49.62

19 -49.907 4.00

20 22.00 1.58913

twenty one

In Table 7, R represents the radius of curvature, d represents the lens thickness or air spacing, Nd represents the refractive index of the d-line (58 nm), and Vd represents the Abbe number of the d-line. Between the subscript R and d and the lens The relationship is as shown in FIG. The symbol f in Table 7 is the focal point of the first lens group G.

1 21 Distance, symbol f is the focal length of the second lens group G, symbol f is the focal length of the third lens group G

2 22 3 23

Indicates.

[0105] Further, in Table 7, the symbol f is the focal length of the short focal end, the symbol f is the focal length of the long focal end, and w t

The symbol f indicates the combined back focus up to the first lens group G force and the third lens group G b 21 23

The

[0106] The projection distance in the third embodiment is 1000 mm. In Table 1, the unit of the numerical value indicating the distance is not specified !, and in all cases it is mm.

[0107] According to the zoom lens of Numerical Example 1, it is possible to provide a projection zoom lens having eight lens elements, which is smaller than the conventional zoom lens. In this description, for the cemented lens that is a component of the group, the entire cemented lens is calculated as one lens. In addition, as shown in Table 1, the zoom lens of Numerical Example 1 maintains telecentricity.

[0108] The zoom lens of the third embodiment can be used as a projection lens of a projector.

(Configuration of Numerical Example 2 in the Third Embodiment)

Next, FIG. 29 shows a configuration of a zoom lens according to Numerical Example 2 of the third embodiment. In the description of Numerical Example 2, the same reference numerals are used for the same constituent elements and characteristics as those of Numerical Example 1 to simplify the description.

[0110] Various aberrations of Numerical Example 2 are shown in FIGS. Figure 30 shows various aberrations at the short focal end.

31 shows various aberrations at the intermediate focal position, and FIG. 32 shows various aberrations at the long focal end. Table 8 shows the characteristics of Numerical Example 2.

[0111] [Table 8] R d Nd Vd

1 131.0658 2.00 1.80420 46.50

2 30.5760 13.01

3 -182.1067 8.00 1.80518 25.46

4 -41.2759 1.00

5 -45.8909 5.00 1.48749 70.44

6 42.6480 40.68

7 · 7.82

8 242.4800 3.20 1.80420 46.50

9 -99.5525 1.50

10 37.9283 1.30 1.80518 25.46

11 20.2581 4.52 1.72000 43.90

12 117.9600 19.85

13 32.0721 1.00 1.84666 23.78

14 18.9125 4.55 1.48749 70.44

15 -52.5715 1.24

16 -42.1738 1.30 1.48749 70.44

17 21.4747 10.18

18 47.6799 3.39 1.77250 49.62

19 -67.5253 4.00

20 oo 22.00 1.58913

21 oo

The other configurations and advantages of the numerical value embodiment 2 are basically the same as those of the numerical value example 1, and thus detailed description thereof is omitted.

(Configuration of Numerical Example 3 in the Third Embodiment) Next, FIG. 33 shows a configuration of a zoom lens according to Numerical Example 3 of the third embodiment. In the description of Numerical Example 3, the same reference numerals are used for the same components and characteristics as those of Numerical Example 1 to simplify the description.

Various aberrations of Numerical Example 3 are shown in FIGS. Figure 34 shows various aberrations at the short focal end.

35 is a diagram of various aberrations at the intermediate focal position, and FIG. 36 is a diagram of various aberrations at the long focal point. In addition, Table 9 shows the characteristics of Numerical Example 3.

[0115] [Table 9]

R d Nd Vd

1 111.5490 2.00 1.80420 46.50

2 28.5662 19.61

3 -42.9438 8.00 1.80518 25.46

4 -32.8929 1.66

5 -37.8780 5.00 1.48749 70.44

6 -88.6820 45.00

7 00 8.39

8 214.7366 3.11 1.80420 46.50

9 -117.6225 1.50

10 32.2729 1.30 1.80518 25.46

11 18.4092 4.99 1.72000 43.90

12 110.8199 18.25

13 33.7817 1.00 1.84666 23.78

14 16.3758 4.51 1.48749 70.44

15 -127.7361 1.2

16 -38.66 / 5 1.30 1.48749 70.44

17 19.6610 8.38

18 40.7623 3.95 1.77250 49.62

19 -51.5099 4.00

20 00 22.00 1.58913

21 00

Jl

Since the other configurations and advantages of Numerical Example 3 are basically the same as those of Numerical Example 1, further detailed explanation is omitted. The present invention is not limited to the above-described embodiments and examples, and various modifications can be made without departing from the gist of the present invention.

Claims

The scope of the claims

[1] The first lens group, the second lens group, the third lens group, and the fourth lens group are arranged in order from the projection surface side, and are arranged between the short focal end and the long focal end. A zoom lens capable of zooming,

The first lens group is composed of three lenses, a negative lens, a positive lens, and a negative lens, in order from the projection surface side, and has negative power.

The second lens group includes, in order from the projection surface side, a total of three lenses including one cemented lens or one positive lens, one positive lens or one cemented lens, and one cemented lens. It consists of a lens and has positive power.

The third lens group is composed of one negative lens,

The fourth lens group is composed of one positive lens,

Further, when zooming, the first lens group and the second lens group are moved, and the third lens group and the fourth lens group are fixed, and The zoom lens is characterized in that the third lens group is configured to be moved for focusing.

[2] The zoom lens according to [1], wherein the following conditional expression (1) is satisfied.

0.7≤ I f / f I ≤1.5 (1)

twenty one

Where f is the composite focal length of the first lens unit

f: Composite focal length of the second lens group

2

[3] The zoom lens according to claim 1 or 2, further satisfying the following conditional expression (2):

1.5≤ I f / f

b w I ≤2.5 (2)

b

f: Focal length at short focal end

w

[4] The zoom lens according to any one of claims 1 to 3, further satisfying the following conditional expression (3):

0.08≤ I f / f I ≤0.3 (3) Where f is the composite focal length of the third lens group

Three

f: Focal length at long focal end

T

[5] A zoom lens that is composed of a first lens group, a second lens group, and a third lens group in order from the projection surface side, and that can change the magnification between the short focal end and the long focal end. Because

The second lens group is arranged in order from the projection surface side.

One positive lens,

One cemented lens composed of two lenses,

With one cemented lens composed of two lenses

It consists of a total of 3 lenses and has positive power.

The third lens group is composed of two lenses of a negative lens and a positive lens in order from the projection surface side and has a positive power.

Further, when zooming, the first lens group and the second lens group are moved, and the third lens group is fixed,

Furthermore, the zoom lens is characterized in that the third lens group is configured to be moved for focusing.

6. The zoom lens according to claim 5, further satisfying the following conditional expression (1).

0.6≤ I f / f

2 1 I ≤1.3 (1)

Where f is the composite focal length of the first lens unit

f: Composite focal length of the second lens group

2

[7] The zoom lens according to claim 5 or 6, further satisfying the following conditional expression (2):

0. 8≤ I f / ϊ I ≤1. 8 (2)

b w

b

f: Focal length at short focal end

w

[8] Furthermore, the following conditional expression (3) is satisfied, Any one of claims 5 to 7, Zoom lens described in 1.

0.08≤ I f / f I ≤0.3 (3)

t 3

Where f is the focal length of the long focal end

f: Composite focal length of the third lens group

Three

A projector comprising the zoom lens according to any one of claims 1 to 8.